Electric power state estimation plays an important role in monitoring and controlling power systems. These estimations are used for network security purposes, optimization purposes and for use by dispatchers. The measurement set for estimation in the prior art factor voltage magnitude, branch real and reactive power flow, real and reactive power injection and/or ampere magnitude. Some recent developments have included voltage phase angle measurement as an additional factor.
It has shown to be difficult to properly tune the error for voltage phase angle measurement. As this measurement error is an essential input to state estimation, this significantly affects state estimator output results and convergence robustness. Changes in the system frequency and loss of phase angle reference may have a significant negative impact on the angle measurement accuracy. Furthermore, previous attempts at using voltage phase angle measurement did not take advantage of the availability of complex bus voltage and complex current in each branch that is adjacent to the bus. Failure to use the complex bus voltage and complex current significantly reduced a system's capability of improving measurement redundancy and ensuring observability in otherwise unobservable areas. Finally, equations used in prior art state estimation models did not include phase angle measurements, which would require the development of a new equation type.
The references below disclose the basic principles related to phasor measurement utilizations in state estimation in the prior art. Previous attempts to introduce phasors to state estimation are based on such principles. “Implementation of phasor measurements in state estimator at Sevillana de Electricidad”, by Slutsker et al. (Power Industry Computer Application Conference, 1995, Conference Proceedings, 1995 IEEE, 7-12 May 1995 Page(s): 392-398 Digital Object Identifier 10.1109/PICA.1995.515269) discloses an implementation of phase angle measurements in an industrial state estimator using enhancements to the state estimator algorithm. “Improved Bad Data Processing via Strategic Placement of PMUs” by Chen et al. (Power Engineering Society General Meeting, 2005, IEEE 12-16 Jun. 2005 Page(s): 509-513 Vol. 1 Digital Object Identifier 10.1109/PES.2005.1489694) discloses a placement algorithm for using phasor measurement units to detect bad data in a state estimator.